Heretofore, as a method for producing an aromatic compound by substituting the sulfonic acid group in a sulfonic acid aromatic-ester with a hydrogen atom, known is a method of substituting the sulfonic acid group in a trifluoromethanesulfonate with a hydrogen atom by reacting a trifluoromethanesulfonate with magnesium in the presence of a platinum group metal (see Patent Reference 1 and Non-Patent Reference 1).
However, the method requires metal magnesium in an amount of not smaller than the equimolar amount of the sulfonate and metal magnesium does not dissolve in the reaction liquid, and therefore the method has some problems in that the operability is poor, the reaction control is difficult and the sulfonate concentration could not be increased. In addition, there is a possibility that the inner wall of the reactor may be damaged by metal magnesium and the plumbing may be clogged. Further, according to the method, in case where the alkyl moiety in the sulfonic acid group is an electron-deficient group such as a trifluoromethanesulfonic acid group, it is known that the ester is hydrolyzed and the reaction yield could not increase (see Non-Patent Reference 2, p. 1270).
In addition, Non-Patent Reference 2 discloses, as a method for producing an aromatic compound by substituting the sulfonic acid group in a sulfonic acid aromatic-ester with a hydrogen in the presence of a platinum group metal not using metal magnesium, a method of using a hydrogen gas and an amine compound such as diethylamine as a reducing agent.
However, according to the method, it is shown that, in a sulfonic acid aromatic-ester where three methoxy groups that are electron-donating groups substitute on the aromatic group, the sulfonic acid group such as a methanesulfonic acid group could not almost substituted with a hydrogen atom, and it is shown that the sulfonic acid group to which the method is applicable is limited only to an electron-deficient group such as a trifluoromethanesulfonic acid group. In addition, in the method, a hydrogen gas is used and therefore devices of a hydrogen cylinder, a regulator, a flow meter and the like are necessary, which require strict safety control.    [Patent Reference 1] JP-A 2005-239595    [Non-Patent Reference 1] Sajiki, H., et al.; Organic Letters, 2006, 8, 5, 987    [Non-Patent Reference 2] Mori, A., et al.; Tetrahedron, 2006, 63, 1270